Nursing care
Insulin Glargine: what to check before you give it
Written and reviewed by Dana Whitfield, RN, MSN · 4 min read · Updated September 2026
Short answer
Insulin glargine is a long-acting basal insulin with no pronounced peak, given once daily at the same time to provide steady background coverage. It must never be mixed in the same syringe with any other insulin, as doing so disrupts its release profile. Hypoglycaemia is the main risk to monitor, though its flat profile makes it less likely than with peaked insulins.
Mechanism, simply
Insulin glargine forms microprecipitates in the subcutaneous tissue after injection, which dissolve slowly and release the drug steadily over roughly 24 hours. The result is a flat, prolonged profile with no pronounced peak, unlike rapid or intermediate-acting insulins that rise and fall within hours.
This no-peak characteristic is the defining fact to hold onto with this drug. It is designed to mimic basal insulin secretion, the background level the body produces independent of meals, rather than covering the glucose rise from a specific meal. That is why it is given once daily at a fixed time rather than dosed around food.
Indications you will see on the ward
Glargine is used for both type 1 and type 2 diabetes as the basal component of a basal-bolus regimen, or sometimes alone in type 2 disease where oral agents are no longer sufficient. It provides the steady background insulin level that rapid-acting insulin at mealtimes is layered on top of.
You will see it prescribed under brand names including Lantus, Basaglar, and Toujeo, with Toujeo being a more concentrated formulation that is not interchangeable unit-for-unit with standard glargine without prescriber-directed conversion. Confirm which formulation and brand is on the chart before administering, since dosing and concentration differ between them.
Assessment before administration
Check the most recent blood glucose and confirm it aligns with the prescribed dose and any sliding scale or correction protocol in use, though glargine itself is a fixed basal dose rather than a sliding scale insulin. Review the administration time against the patient's usual schedule, since consistency of timing matters more with this drug than with most other medications on the chart.
Inspect the injection site and rotate through the abdomen, thigh, or upper arm to reduce lipohypertrophy over repeated doses. Confirm the insulin is clear and colourless, since any cloudiness or precipitate suggests the product should not be used. Verify independently, with a second nurse where your facility requires it, given how commonly insulin errors are implicated in harm reports.
Toxicity and the antidote
The primary toxicity risk is hypoglycaemia, presenting as diaphoresis, tremor, tachycardia, confusion, and, if untreated, seizure or loss of consciousness. Because glargine has no peak, hypoglycaemia is less predictable in timing than with peaked insulins and can occur at any point across the 24-hour dosing interval, so ongoing vigilance matters more than watching a specific window.
There is no pharmacological antidote in the sense of a receptor blocker. Treatment is oral fast-acting carbohydrate for a conscious patient able to swallow, or intramuscular or subcutaneous glucagon and intravenous dextrose for a patient who is unconscious or unable to take oral glucose. Recheck blood glucose 15 minutes after treatment and repeat as needed until it stabilises above the treatment threshold set by your facility protocol.
Interactions that matter
Other glucose-lowering agents, including oral antidiabetics and other insulins, increase hypoglycaemia risk when combined, so any dose adjustment on the chart should prompt closer glucose monitoring for a period afterward. Beta-blockers can mask the adrenergic warning signs of hypoglycaemia, such as tremor and tachycardia, leaving confusion or diaphoresis as the main clues in a patient on these drugs.
Corticosteroids and some diuretics raise blood glucose and can reduce glargine's effectiveness at a given dose, which may prompt a prescriber to adjust the regimen. Alcohol can potentiate hypoglycaemia, which is worth covering in discharge teaching rather than assuming the patient already knows.
What the patient must be told
Glargine is given once a day at the same time, and this consistency is not a minor preference but central to how the drug works to provide steady coverage. Missing the usual time by a couple of hours is generally manageable, but the patient should be taught to ask their prescriber how to handle a significant delay or a missed dose rather than guessing.
It is never mixed in the same syringe with any other insulin or drug, which is a hard rule rather than a convenience recommendation, since mixing disrupts the mechanism that gives glargine its flat profile. Teach the patient to recognise hypoglycaemia symptoms, keep a fast-acting glucose source on hand, rotate injection sites, and store unopened pens refrigerated while the pen in current use is kept at room temperature per the manufacturer's stated duration.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our endocrine practice questions are the closest set to what this page covers.
Common questions
Why is insulin glargine given once a day?
It forms a slow-release depot under the skin that provides a steady, roughly 24-hour basal insulin level with no pronounced peak. Once-daily dosing at a consistent time maintains that steady background coverage.
Can insulin glargine be mixed with other insulin in the same syringe?
No. Mixing glargine with any other insulin disrupts its release mechanism and unpredictable results. It is always drawn up and administered separately.
Does insulin glargine have a peak action time?
No, it is designed to have a flat, peakless profile over its duration of action. This is different from intermediate or rapid-acting insulins and is why hypoglycaemia timing is less predictable with glargine.
What do you give for hypoglycaemia caused by insulin glargine?
Oral fast-acting carbohydrate if the patient is conscious and able to swallow, or glucagon with intravenous dextrose if they are not. Recheck blood glucose 15 minutes after treatment and repeat as needed.
Is Lantus the same as insulin glargine?
Lantus is a brand name for insulin glargine. Other brands include Basaglar and the more concentrated Toujeo, which is not unit-for-unit interchangeable with standard glargine without prescriber guidance.